I do believe RJ is bisexual, because why would he "lie" about that. However, I understand the point of view that -- at least to my knowledge -- I have never seen (or heard) anything in his content -- sex or other -- that indicates that he is even remotely into women, besides him saying he's bi. Never a simple "I think she's hot." It's always been male-focused.
Again, I do believe he is bisexual, simply because he said he is, and who am I to question it then? But maybe we can at least agree that his focus has been male-oriented